In National Security Action Memorandum No. 311 (NSAM 311), President Johnson ordered Secretary of State Dean Rusk, Secretary of Defense Robert McNamara, and Director of Central Intelligence John McCone to review the prospect of a repeat of the Cuban Missile Crisis and to outline the various alternatives that would be available if it happened.
Date: July 10, 1964
Author: McGeorge Bundy
Title: NSAM 311: Review of the Problem of Assurance Against Any Missile Crisis in Cuba
Archival Source: "NSAM 311-Review of the Problem of Assurance Against Any Missile Crisis in Cuba" folder, Box 5, National Security File: NSAM, Lyndon B. Johnson Library
A copy of the some of the findings are available here. Other related documents remain pending declassification review.